Laser Capture Microdissection is a technique developed at NIH to capture minute portions of tissue from histo-pathology slides for subsequent molecular analysis. A thermoplastic film in contact with a tissue specimen is selectively activated by a laser beam under microscopic control to bond with the desired tissue. Removal of the film separates the adhered tissue from that remaining on the slide, making it available for analysis. The technique enables the collection and processing of extremely homogeneous samples in a routine manner that does not require great manual dexterity. Over the past several years a number of refinements of the technique have been developed. A cylindrical configuration employing a "line" contact with the tissue has been perfected which minimizes contamination, and is capable of removing tissue fragments as small as 3 microns in diameter. Several systems utilizing a continuous tape of thermoplastic are under development. A thermal model has been developed to describe the process by which the laser energy is absorbed and diffused in the polymer. This enables the prediction of tissue and film temperature transients as a function of the system parameters.